This invention relates to an electrical switch assembly and, more particularly, to such an assembly which may be used in an automobile to automatically control the raising or lowering of a window to an extreme position thereof in response to a momentary operation of the switch assembly actuator button.
In an automobile having motor driven windows, it is often desired to drive a window to an extreme position, either fully opened or fully closed. This of course may be accomplished by the operator continuously operating the window switch. However, it would be desirable to provide a switch assembly wherein only a single momentary operation of the switch assembly actuator button is required to cause the motor to be driven to an extreme position. It is therefore a primary object of the present invention to provide a switch assembly having such capability.
In the past, it has been proposed to implement this function in a number of different ways. A straightforward approach is to utilize limit switches for sensing travel of the window to an extreme position. This approach is unsatisfactory in that it requires additional parts, thereby significantly increasing the cost. Other approaches have utilized the principle that the motor will stall when the window reaches its extreme position, which results in an increase in the motor current. Some of these approaches have included circuitry for sensing the motor current and opening the current path when the motor current exceeds a predetermined threshold. Again, this is disadvantageous in that it requires additional circuity which increases the cost. Still other approaches have utilized a bi-metallic element which opens the switch when it is heated by excessive motor current flowing therethrough. This too is disadvantageous because the bi-metallic element is sensitive to ambient temperature and cannot be operated repeatedly without a cool down period between operations. Yet another approach is to use a magnetic latch in conjunction with a timing circuit where the timer is set to time an interval greater than that required to drive the window to its extreme position, at the end of which interval the latch is deenergized. This approach is disadvantageous due to its complexity and cost. It is therefore another object of the present invention to provide a switch assembly without any of the noted disadvantages.
It is a further object of this invention to provide such a switch assembly which is small and self contained so that it does not require additional wire harnesses.
It is yet another object of the present invention to provide such a switch assembly which is automatically unlatched upon the removal of power so that the window drive is not energized when power is initially applied.
It is yet another object of the present invention to provide such a switch assembly which is also sensitive to the window being inadvertently stopped by an obstruction at some middle position.